2.2. The Primary Rate Interface

• 2.2.1. Benefits of PRI
• 2.2.2. PRI Configurations and Applications
• Terminate Configuration Applications
• Drop-and-Insert Configuration Applications

The Dialogic Primary Rate Interface (PRI) product line enables SCbus applications to use the speed, power, and flexibility of ISDN. The Dialogic PRI firmware supports both T-1 and E-1 protocols.

The T-1 protocol implementations comply with the North American standard ISDN Primary Rate and the INS-1500 standard used in Japan. In North America and Japan, the Primary Rate includes 23 voice/data channels (B channels) and one signaling channel (D channel).

The E-1 protocol implementations comply with the E-1 Primary Rate interface protocol. The E-1 ISDN Primary Rate includes 30 voice/data channels (B channels) and two additional channels: one signaling channel (D channel) and one framing channel to handle synchronization.

See Section 2.3. Dialogic ISDN Protocol Support for specific supported T-1 and E-1 protocols.

2.2.1. Benefits of PRI

ISDN Primary Rate technology offers the benefits inherent in digital connectivity, such as fast call connection (setup and teardown), fast Dialed Number Identification Service (DNIS), and fast Automatic Number Identification (ANI) acquisition. These features support applications such as speed dialing, automated operator services, call waiting, call forwarding, and geographic analysis of customer databases.

ISDN PRI applications also can take advantage of the following features offered by the network:

• Two B-Channel Transfer (TBCT). Enables a user to request the switch to connect together two independent calls on the user's interface. The user who made the request is released from the calls and the other two users are directly connected. This feature is supported for 5ESS, 4ESS, and National ISDN-2 (NI2) protocols. For more on TBCT, see Appendix A - Call Control Scenarios.
• Non-Call Associated Signaling (NCAS). Allows users to communicate by means of user-to-user signaling without setting up a circuit-switched connection (it does not occupy B channel bandwidth). A temporary signaling connection is established and cleared in a manner similar to the control of a circuit-switched connection. This feature is supported for the 5ESS protocol. For more on NCAS, see Appendix A - Call Control Scenarios.
• Vari-A-Bill. A flexible billing option enabling a customer to modify the charge for a call while the call is in a stable state (for example, between answer and disconnect). This feature is available from the AT&T network only.
• ANI-on-demand. Allows the user to request a caller ID number to identify the origin of the call, when necessary.
• Non-facility Associated Signaling (NFAS). Provides support for multiple ISDN spans from a single D channel. The NFAS D channel is supported only on the DTI/240SC and DTI/300SC products.
• User-to-user information. An information element that may be included in setup, connect, or disconnect messages.
• Call-by-Call service selection. This feature allows the user to access different services, such as an 800 line or a WATS line, on a per call basis.
• LAP-D Layer 2 (Data Link Layer) access. This feature allows access to the data link layer, providing for the reliable transfer of data across the physical link (physically connected devices), and sending blocks of frames with the necessary synchronization, error control, and flow control. Layer 2 access is particularly useful when using a Dialogic ISDN board to connect to a switch using a Layer 3 protocol that is not provided in the firmware.

The following sections describe the PRI configurations required to support various ISDN applications.

2.2.2. PRI Configurations and Applications

Using the Dialogic ISDN Primary Rate product, software applications operating in the host PC can control Primary Rate line connectivity. The boards can be configured as terminating devices or installed in a variety of drop-and-insert configurations.

In a terminating configuration, incoming or outgoing calls on ISDN lines are processed by supported resource boards (such as voice boards). In a drop-and-insert configuration, incoming and outgoing calls (on individual channels) can either be processed by supported resource boards or passed on to additional network boards. Calls can also be both processed by supported resource boards and passed on to additional network boards, as well.

The following sections contain examples of typical applications for terminate and drop-and-insert configurations.

Terminate Configuration Applications

Dialogic ISDN products in a terminate configuration with one or more resource boards (for example, voice boards) allow for the development of a variety of applications, such as the following:

• Audiotex applications allow users to retrieve and listen to pre-recorded messages over the telephone. In some simpler applications, the user's only action is to initiate the call. More complex applications may require the user to respond to one or more prompts using, for example, the touch tone keys on the telephone.
• Telemarketing applications use voice processing technology to facilitate a high volume of inbound/outbound calls. The calls depend upon an operator-assisted transaction and/or are motivated by a specific event, such as the need to quickly distribute a promotional or informational message to a targeted audience of phone users.
• Host Interactive Voice Response (HIVR) applications enable fully automated transaction processing or transaction passing to occur over the telephone. Examples of these applications include, but are not limited to, banking by phone, order entry systems, and inventory control services.
• Central Office (CO) Voice Mail applications include many kinds of solutions which enable users to store and forward or record and retrieve voice messages. These applications may be simple and operate like an answering machine, or they may be more complex and include automated attendant functions.

Drop-and-Insert Configuration Applications

Dialogic ISDN products can be placed in a variety of drop-and-insert configurations, providing all the features and benefits of terminate configurations, plus the ability to access an operator or another call. Drop-and-insert configurations allow calls to be passed from one network module to another network module. The following types of applications are provided by drop-and-insert configurations:

• Operator Services applications are able to automate large numbers of telephone calls that require some kind of caller assistance. Such applications include, but are not limited to, partially automated directory assistance, calling card voice prompting, and collect calls.
• Telemarketing applications depend on a specific event/transaction. The primary difference between telemarketing applications in a terminate configuration and telemarketing applications in a drop-and-insert configuration is that the latter allow for the use of an existing PBX and telephone equipment.
• Protocol Conversion is a drop-and-insert configuration, without resource boards, used to convert calls from one network protocol to another network protocol.

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